Wafer

ABSTRACT

A wafer includes a substrate layer, a first mirror layer having a plurality of two-dimensionally arranged first mirror portions, and a second mirror layer having a plurality of two-dimensionally arranged second mirror portions. A plurality of Fabry-Perot interference filter portions are formed in an effective area, in each of the plurality of Fabry-Perot interference filter portions a gap is formed between the first mirror portion and the second mirror portion. A plurality of dummy filter portions are formed in a dummy area disposed along an outer edge of the substrate layer and surrounding the effective area, in each of the plurality of dummy filter portions an intermediate layer is provided between the first mirror portion and the second mirror portion. At least the second mirror portion is surrounded by the first groove in each of the plurality of Fabry-Perot interference filter portions and the plurality of dummy filter portions.

TECHNICAL FIELD

The present disclosure relates to a wafer for obtaining a Fabry-Perotinterference filter.

BACKGROUND ART

In the related art, a Fabry-Perot interference filter including asubstrate, a fixed mirror and a movable mirror facing each other via agap on the substrate is known (for example, refer to Patent Literature1).

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Unexamined Patent Publication No.    2013-506154

SUMMARY OF INVENTION Technical Problem

Since a Fabry-Perot interference filter as described above is a finestructure, it is difficult to improve both manufacturing efficiency anda yield when a Fabry-Perot interference filter is manufactured.

Therefore, the present disclosure aims to provide a wafer capable ofobtaining a plurality of Fabry-Perot interference filters with highefficiency and high yield.

Solution to Problem

A wafer according to one aspect of the present disclosure includes: asubstrate layer having a first surface and a second surface opposite tothe first surface; a first mirror layer having a plurality of firstmirror portions two-dimensionally arranged on the first surface; and asecond mirror layer having a plurality of second mirror portionstwo-dimensionally arranged on the first mirror layer, in which aplurality of Fabry-Perot interference filter portions are formed in aneffective area, in each of the plurality of Fabry-Perot interferencefilter portions a gap is formed between the first mirror portion and thesecond mirror portion facing each other and a distance between the firstmirror portion and the second mirror portion facing each other varies byan electrostatic force, a plurality of dummy filter portions are formedin a dummy area disposed along an outer edge of the substrate layer andsurrounding the effective area, in each of the plurality of dummy filterportions an intermediate layer is provided between the first mirrorportion and the second mirror portion facing each other, and at leastthe second mirror portion is surrounded by a first groove opening on aside opposite to the substrate layer in each of the plurality ofFabry-Perot interference filter portions and the plurality of dummyfilter portions.

In this wafer, a plurality of Fabry-Perot interference filter portionsto be a plurality of Fabry-Perot interference filters is provided in theeffective area. In addition, a plurality of dummy filter portions isprovided in the dummy area desposed along an outer edge of the substratelayer and surrounding the effective area. In each of the dummy filterportions, an intermediate layer is provided between the first mirrorportion and the second mirror portion facing each other. Thisconfiguration sufficiently ensures the strength of the entire wafer.This facilitates handling of the wafer when cutting out a plurality ofFabry-Perot interference filters from the wafer, for example. Thepresence of a gap formed between the first mirror portion and the secondmirror portion facing each other in each of the dummy filter portionswould lead to a case, for example, where the second mirror portion isdamaged when the dummy area of the wafer is gripped by a gripper tooland then fragments of the second mirror portion would adhere to theFabry-Perot interference filter portion to degrade the appearance andcharacteristics of the Fabry-Perot interference filter portion. Thiswafer includes an intermediate layer provided between the first mirrorportion and the second mirror portion facing each other in each of thedummy filter portions, and thus, such a situation is suppressed. In eachof the Fabry-Perot interference filter portions, at least the secondmirror portion is surrounded by the first groove. This improves theyield in cutting out a plurality of Fabry-Perot interference filtersfrom the wafer. Furthermore, at least the second mirror portion issurrounded by the first groove in each of the dummy filter portions.This can reduce the stress in the dummy area, suppressing the warpage ofthe wafer. The configuration of the wafer as described above makes itpossible to obtain a plurality of Fabry-Perot interference filters withhigh efficiency and with high yield.

In the wafer according to one aspect of the present disclosure, thefirst groove may be continuous through the effective area and the dummyarea and may reach an outer edge of the substrate layer when viewed inthe direction in which the first mirror portion and the second mirrorportion face each other. With this configuration, it is possible tofurther improve the yield at the time of cutting out a plurality ofFabry-Perot interference filters from the wafer and possible to furtherreliably suppress the warpage of the wafer.

The wafer according to one aspect of the present disclosure may furtherinclude a stress adjustment layer provided on the second surface, secondgroove opening on the opposite side of the substrate layer may be formedin the stress adjustment layer, and the second groove may be formed soas to correspond to the first groove. With this configuration, it ispossible to further improve the yield at the time of cutting out aplurality of Fabry-Perot interference filters from the wafer andpossible to further reliably suppress the warpage of the wafer.

In the wafer according to one aspect of the present disclosure, theplurality of Fabry-Perot interference filter portions and the pluralityof dummy filter portions may be disposed so as to be symmetric abouteach of a first straight line and a second straight line passing throughthe center of the substrate layer and orthogonal to each other whenviewed in the direction in which the first mirror portion and the secondmirror portion face each other. This makes it possible to more reliablysuppress the warpage of the entire wafer.

In the wafer according to one aspect of the present disclosure, amodified region may be formed inside the substrate layer so as tocorrespond to the first groove. This enables extension of a fracturefrom the modified region in a thickness direction of the substratelayer, making it possible to easily and accurately cut out a pluralityof Fabry-Perot interference filters from the wafer.

The wafer according to one aspect of the present disclosure may furtherinclude an expanding tape attached to a second surface side with respectto the substrate layer. This facilitates wafer handling even in a statewhere the modified region is formed inside the substrate layer.

In the wafer according to one aspect of the present disclosure, amirror-removed portion is formed in a portion of the dummy area, in themirror-removed portion at least a portion of the second mirror portionmay be removed. With this configuration, in a case where a plurality ofthrough-holes is to be formed in the second mirror portion in a portioncorresponding to each of the Fabry-Perot interference filter portions inorder to form a gap by etching between the first mirror portion and thesecond mirror portion facing each other, for example, it is possible, bymonitoring the removal state of the second mirror portion in a portioncorresponding to the mirror-removed portion, to reliably form theplurality of through-holes in the second mirror portion at a portioncorresponding to each of the Fabry-Perot interference filter portions.This makes it possible to achieve a wafer including a plurality ofFabry-Perot interference filter portions, each of the plurality ofFabry-Perot interference filter portions in which a gap is reliablyformed between the first mirror portion and the second mirror portionfacing each other.

In the wafer according to one aspect of the present disclosure, at leastthe first mirror portion may be surrounded by the first groove in themirror-removed portion. This can reduce the stress also in themirror-removed portion, suppressing the warpage of the wafer.

In the wafer according to one aspect of the present disclosure, themirror-removed portions may be provided in plurality along the outeredge of the substrate layer in the dummy area, the first groove may becontinuous through the effective area and the dummy area and may reachthe outer edge of the substrate layer when viewed in the direction inwhich the first mirror portion and the second mirror portion face eachother. With this configuration, the plurality of dummy filter portionsis arranged outside the plurality of Fabry-Perot interference filterportions, and the plurality of mirror-removed portions is arrangedoutside the plurality of dummy filter portions, and the first groove isalso continuous to reach the outer edge of the substrate layer, leadingto improvement of the stress balance of the entire wafer, making itpossible to further reliably suppress the warpage of the wafer.

Advantageous Effects of Invention

According to the present disclosure, it is possible to provide a wafercapable of obtaining a plurality of Fabry-Perot interference filterswith high efficiency and high yield.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of a Fabry-Perot interference filter cut out froma wafer according to an embodiment.

FIG. 2 is a bottom view of a Fabry-Perot interference filter illustratedin FIG. 1.

FIG. 3 is a cross-sectional view of the Fabry-Perot interference filtertaken along line in FIG. 1.

FIG. 4 is a cross-sectional view of a dummy filter cut out from a waferaccording to an embodiment.

FIG. 5 is a plan view of a wafer according to an embodiment.

FIG. 6 is an enlarged plan view of a portion of the wafer illustrated inFIG. 5.

FIG. 7 is a cross-sectional view of a Fabry-Perot interference filterportion and a dummy filter portion of the wafer illustrated in FIG. 5.

FIG. 8 is a cross-sectional view illustrating a method for manufacturingthe wafer illustrated in FIG. 5.

FIG. 9 is a cross-sectional view illustrating a method for manufacturingthe wafer illustrated in FIG. 5.

FIG. 10 is a cross-sectional view illustrating a method formanufacturing the wafer illustrated in FIG. 5.

FIG. 11 is a cross-sectional view illustrating a method formanufacturing the wafer illustrated in FIG. 5.

FIG. 12 is a cross-sectional view illustrating a method formanufacturing the wafer illustrated in FIG. 5.

FIG. 13 is a cross-sectional view illustrating a method formanufacturing the wafer illustrated in FIG. 5.

FIG. 14 is a cross-sectional view illustrating a method for cutting outa Fabry-Perot interference filter from the wafer illustrated in FIG. 5.

FIG. 15 is a cross-sectional view illustrating a method for cutting outa Fabry-Perot interference filter from the wafer illustrated in FIG. 5.

FIG. 16 is a cross-sectional view of a light detection device includinga Fabry-Perot interference filter.

FIG. 17 is a plan view of a wafer according to a modification.

FIG. 18 is a cross-sectional view illustrating a method formanufacturing the wafer illustrated in FIG. 17.

FIG. 19 is a cross-sectional view illustrating a method formanufacturing the wafer illustrated in FIG. 17.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present disclosure will be describedin detail with reference to the drawings. In all the drawings, the sameor equivalent portions are denoted with the same reference numerals andduplicated description is omitted.

[Configuration of Fabry-Perot Interference Filter and Dummy Filter]

Prior to the description of the configuration of the wafer of oneembodiment, the configuration of each of the Fabry-Perot interferencefilter and the dummy filter cut out from the wafer will be described.

As illustrated in FIGS. 1, 2, and 3, a Fabry-Perot interference filter 1includes a substrate 11. The substrate 11 has a first surface 11 a and asecond surface 11 b opposite to the first surface 11 a. On the firstsurface 11 a, a reflection prevention layer 21, a first laminate 22, anintermediate layer 23, and a second laminate 24 are laminated in thisorder. A gap (air gap) S is defined between the first laminate 22 andthe second laminate 24 by the frame-shaped intermediate layer 23.

The shape and the positional relationship of individual portions whenviewed in a direction perpendicular to the first surface 11 a (planview) are as follows. The outer edge of the substrate 11 has arectangular shape with a side being several hundred μm to several mm.The outer edge of the substrate 11 and an outer edge of the secondlaminate 24 are aligned with each other. An outer edge of the reflectionprevention layer 21, an outer edge of the first laminate 22, and anouter edge of the intermediate layer 23 are aligned with each other. Thesubstrate 11 has an outer edge portion 11 c positioned on an outer sideof the outer edge of the intermediate layer 23 with respect to thecenter of the gap S. For example, the outer edge portion 11 c has aframe shape and surrounds the intermediate layer 23 when viewed in adirection perpendicular to the first surface 11 a. The gap S has acircular shape, for example.

The Fabry-Perot interference filter 1 transmits light having apredetermined wavelength through a light transmission region 1 a definedin a center portion of the Fabry-Perot interference filter 1. The lighttransmission region 1 a is a columnar region, for example. The substrate11 is formed of silicon, quartz, or glass, for example. When thesubstrate 11 is formed of silicon, the reflection prevention layer 21and the intermediate layer 23 are formed of silicon oxide, for example.The thickness of the intermediate layer 23 ranges from several tens ofnm to several tens of μm, for example.

A portion corresponding to the light transmission region 1 a in thefirst laminate 22 functions as a first mirror portion 31. The firstmirror portion 31 is a fixed mirror. The first mirror portion 31 isdisposed on the first surface 11 a via the reflection prevention layer21. The first laminate 22 includes alternate laminations of each of aplurality of polysilicon layers 25 and each of a plurality of siliconnitride layers 26. The Fabry-Perot interference filter 1 includes layersof a polysilicon layer 25 a, a silicon nitride layer 26 a, a polysiliconlayer 25 b, a silicon nitride layer 26 b, and a polysilicon layer 25 claminated on the reflection prevention layer 21 in this order. Theoptical thickness of each of the polysilicon layers 25 and the siliconnitride layers 26 included in the first mirror portion 31 is preferablyan integral multiple of ¼ of a center transmission wavelength. The firstmirror portion 31 may be directly disposed on the first surface 11 awithout interposing the reflection prevention layer 21.

The portion corresponding to the light transmission region 1 a in thesecond laminate 24 functions as a second mirror portion 32. The secondmirror portion 32 is a movable mirror. The second mirror portion 32faces the first mirror portion 31 via the gap S on a side opposite tothe substrate 11 with respect to the first mirror portion 31. Thedirection in which the first mirror portion 31 and the second mirrorportion 32 face each other is parallel to a direction perpendicular tothe first surface 11 a. The second laminate 24 is disposed on the firstsurface 11 a via the reflection prevention layer 21, the first laminate22, and the intermediate layer 23. The second laminate 24 includesalternate laminations of each of the plurality of polysilicon layers 27and each of the plurality of silicon nitride layers 28. The Fabry-Perotinterference filter 1 includes layers of a polysilicon layer 27 a, asilicon nitride layer 28 a, a polysilicon layer 27 b, a silicon nitridelayer 28 b, and a polysilicon layer 27 c laminated on the intermediatelayer 23 in this order. The optical thickness of each of the polysiliconlayer 27 and the silicon nitride layer 28 included in the second mirrorportion 32 is preferably an integral multiple of ¼ of the centertransmission wavelength.

In the first laminate 22 and the second laminate 24, silicon oxidelayers may be used in place of the silicon nitride layers. In addition,examples of the material applicable for each of layers forming the firstlaminate 22 and the second laminate 24 include titanium oxide, tantalumoxide, zirconium oxide, magnesium fluoride, aluminum oxide, calciumfluoride, silicon, germanium, zinc sulfide, or the like. Here, thesurface of the first mirror portion 31 on the gap S side (surface of thepolysilicon layer 25 c) and the surface of the second mirror portion 32on the gap S side (surface of the polysilicon layer 27 a) directly faceeach other via the gap S. Note that an electrode layer, a protectivelayer, or the like (not forming a mirror) may be formed on the surfaceof the first mirror portion 31 on the gap S side and on the surface ofthe second mirror portion 32 on the gap S side. In this case, the firstmirror portion 31 and the second mirror portion 32 face each other viathe gap S with the presence of these interposed layers. In other words,even in such a case, a facing configuration between the first mirrorportion 31 and the second mirror portion 32 via the gap S can beachieved.

A plurality of through-holes 24 b is formed at a portion of the secondlaminate 24 corresponding to the gap S (a portion overlapping the gap Swhen viewed in a direction perpendicular to the first surface 11 a).Each of the through-holes 24 b extends to reach the gap S from a surface24 a of the second laminate 24 opposite to the intermediate layer 23.The plurality of through-holes 24 b is formed so as not to substantiallyinfluence the function of the second mirror portion 32. The plurality ofthrough-holes 24 b is used for forming the gap S by removing a portionof the intermediate layer 23 through etching.

In addition to the second mirror portion 32, the second laminate 24further includes a covering portion 33 and a peripheral edge portion 34.The second mirror portion 32, the covering portion 33, and theperipheral edge portion 34 are integrally formed to have a portion of asame laminated structure and to be continuous to each other. Thecovering portion 33 surrounds the second mirror portion 32 when viewedin a direction perpendicular to the first surface 11 a. The coveringportion 33 covers a surface 23 a of the intermediate layer 23 on a sideopposite to the substrate 11, a side surface 23 b of the intermediatelayer 23 (a side surface on the outer side, that is, a side surface on aside opposite to the gap S side), a side surface 22 a of the firstlaminate 22, and a side surface 21 a of the reflection prevention layer21, so as to reach the first surface 11 a. That is, the covering portion33 covers the outer edge of the intermediate layer 23, the outer edge ofthe first laminate 22, and the outer edge of the reflection preventionlayer 21.

The peripheral edge portion 34 surrounds the covering portion 33 whenviewed in a direction perpendicular to the first surface 11 a. Theperipheral edge portion 34 is positioned on the first surface 11 a inthe outer edge portion 11 c. The outer edge of the peripheral edgeportion 34 is aligned with the outer edge of the substrate 11 whenviewed in a direction perpendicular to the first surface 11 a. Theperipheral edge portion 34 is thinned along an outer edge of the outeredge portion 11 c. That is, the portion along the outer edge of theouter edge portion 11 c in the peripheral edge portion 34 is thinnercompared to other portions excluding the portion along the outer edge ofthe peripheral edge portion 34. In the Fabry-Perot interference filter1, the peripheral edge portion 34 is thinned by removing a portion ofthe polysilicon layer 27 and the silicon nitride layer 28 included inthe second laminate 24. The peripheral edge portion 34 includes: anon-thinned portion 34 a continuous to the covering portion 33; and athinned portion 34 b surrounding the non-thinned portion 34 a. In thethinned portion 34 b, the polysilicon layer 27 and the silicon nitridelayer 28 are removed excluding the polysilicon layer 27 a directlyprovided on the first surface 11 a.

The height from the first surface 11 a to a surface 34 c of thenon-thinned portion 34 a on a side opposite to the substrate 11 is lowerthan the height from the first surface 11 a to the surface 23 a of theintermediate layer 23. The height from the first surface 11 a to thesurface 34 c of the non-thinned portion 34 a ranges from 100 nm to 5000nm, for example. The height from the first surface 11 a to the surface23 a of the intermediate layer 23 ranges from 500 nm to 20000 nm, forexample. The width of the thinned portion 34 b (distance between theouter edge of the non-thinned portion 34 a and the outer edge of theouter edge portion 11 c when viewed in the direction perpendicular tothe first surface 11 a) is 0.01 times the thickness of the substrate 11,or more. The width of the thinned portion 34 b ranges from 5 μm to 400μm, for example. The thickness of the substrate 11 ranges from 500 μm to800 μm, for example.

A first electrode 12 is formed in the first mirror portion 31 so as tosurround the light transmission region 1 a when viewed in a directionperpendicular to the first surface 11 a. The first electrode 12 isformed by doping impurities into the polysilicon layer 25 c to achievelow resistivity. A second electrode 13 is formed in the first mirrorportion 31 so as to include the light transmission region 1 a whenviewed in a direction perpendicular to the first surface 11 a. Thesecond electrode 13 is formed by doping impurities into the polysiliconlayer 25 c to achieve low resistivity. Note that although it ispreferable that the second electrode 13 is sized to include the entirelight transmission region 1 a when viewed in a direction perpendicularto the first surface 11 a, the second electrode 13 may havesubstantially the same size as that of the light transmission region 1a.

A third electrode 14 is formed in the second mirror portion 32. Thethird electrode 14 faces the first electrode 12 and the second electrode13 via the gap S. The third electrode 14 is formed by doping impuritiesinto the polysilicon layer 27 a to achieve low resistivity.

A pair of terminals 15 are provided to face each other across the lighttransmission region 1 a. Each of the terminals 15 is disposed inside athrough-hole from the surface 24 a of the second laminate 24 to thefirst laminate 22. Each of the terminals 15 is electrically connected tothe first electrode 12 through wiring 12 a. For example, each of theterminals 15 is formed with a metal film of aluminum, an alloy thereof,or the like.

A pair of terminals 16 are provided to face each other across the lighttransmission region 1 a. Each of the terminals 16 is disposed inside athrough-hole from the surface 24 a of the second laminate 24 to thefirst laminate 22. Each of the terminals 16 is electrically connected tothe second electrode 13 through wiring 13 a and is electricallyconnected to the third electrode 14 through wiring 14 a. For example,the terminals 16 are formed with a metal film of aluminum, an alloythereof, or the like. The facing direction of the pair of terminals 15and the facing direction of the pair of terminals 16 are orthogonal toeach other (refer to FIG. 1).

A plurality of trenches 17 and 18 is provided on a surface 22 b of thefirst laminate 22. The trench 17 annularly extends to surround aconnection with respect to the terminals 16 in the wiring 13 a. Thetrench 17 electrically insulates the first electrode 12 and the wiring13 a from each other. The trench 18 annularly extends along an inneredge of the first electrode 12. The trench 18 electrically insulates thefirst electrode 12 and an inner region of the first electrode 12 (secondelectrode 13) from each other. Each of the regions within the trenches17 and 18 may be an insulating material or a gap.

A trench 19 is provided on the surface 24 a of the second laminate 24.The trench 19 annularly extends to surround the terminals 15. The trench19 electrically insulates the terminals 15 and the third electrode 14from each other. The region inside the trench 19 may be an insulatingmaterial or a gap.

The second surface 11 b of the substrate 11 includes layers of areflection prevention layer 41, a third laminate 42, an intermediatelayer 43, and a fourth laminate 44 laminated in this order. Thereflection prevention layer 41 and the intermediate layer 43 each have aconfiguration similar to those of the reflection prevention layer 21 andthe intermediate layer 23. The third laminate 42 and the fourth laminate44 each have a laminated structure symmetrical to those of the firstlaminate 22 and the second laminate 24 with respect to the substrate 11.The reflection prevention layer 41, the third laminate 42, theintermediate layer 43, and the fourth laminate 44 have a function ofsuppressing warpage of the substrate 11.

The third laminate 42, the intermediate layer 43, and the fourthlaminate 44 are thinned along an outer edge of the outer edge portion 11c. That is, the portion along the outer edge of the outer edge portion11 c in the third laminate 42, the intermediate layer 43, and the fourthlaminate 44 is thinner compared to other portions excluding the portionalong the outer edge in the third laminate 42, the intermediate layer43, and the fourth laminate 44. In the Fabry-Perot interference filter1, the third laminate 42, the intermediate layer 43, and the fourthlaminate 44 are thinned by removing all of the third laminate 42, theintermediate layer 43, and the fourth laminate 44 in a portionoverlapping the thinned portion 34 b when viewed in a directionperpendicular to the first surface 11 a.

The third laminate 42, the intermediate layer 43, and the fourthlaminate 44 have an opening 40 a so as to include the light transmissionregion 1 a when viewed in a direction perpendicular to the first surface11 a. The opening 40 a has a diameter substantially the same as the sizeof the light transmission region 1 a. The opening 40 a is open on thelight emission side. The bottom surface of the opening 40 a reaches thereflection prevention layer 41.

A light shielding layer 45 is formed on a surface of the fourth laminate44 on the light emission side. For example, the light shielding layer 45is formed of aluminum or the like. A protective layer 46 is formed on asurface of the light shielding layer 45 and an inner surface of theopening 40 a. The protective layer 46 covers outer edges of the thirdlaminate 42, the intermediate layer 43, the fourth laminate 44, and thelight shielding layer 45 and covers the reflection prevention layer 41on the outer edge portion 11 c. For example, the protective layer 46 isformed of aluminum oxide. An optical influence due to the protectivelayer 46 can be disregarded by forming the protective layer 46 in thethickness ranging from 1 nm to 100 nm (preferably, approximately 30 nm).

In the Fabry-Perot interference filter 1 configured as described above,when a voltage is applied between the first electrode 12 and the thirdelectrode 14 via the pair of terminals 15 and 16, an electrostatic forcecorresponding to the voltage is generated between the first electrode 12and the third electrode 14. The second mirror portion 32 is attracted tothe first mirror portion 31 side secured to the substrate 11 due to theelectrostatic force, and the distance between the first mirror portion31 and the second mirror portion 32 is adjusted. In this manner, in theFabry-Perot interference filter 1, the distance between the first mirrorportion 31 and the second mirror portion 32 varies due to theelectrostatic force.

The wavelength of light to be transmitted through the Fabry-Perotinterference filter 1 depends on the distance between the first mirrorportion 31 and the second mirror portion 32 in the light transmissionregion 1 a. Therefore, the wavelength of light to be transmitted throughthe Fabry-Perot interference filter 1 can be appropriately selected byadjusting the voltage to be applied between the first electrode 12 andthe third electrode 14. At this time, the second electrode 13 has thesame potential as that of the third electrode 14. Therefore, the secondelectrode 13 functions as a compensation electrode to keep the firstmirror portion 31 and the second mirror portion 32 flat in the lighttransmission region 1 a.

In the Fabry-Perot interference filter 1, for example, a spectroscopicspectrum can be obtained by detecting light transmitted through thelight transmission region 1 a of the Fabry-Perot interference filter 1using a light detector while changing the voltage to be applied to theFabry-Perot interference filter 1 (that is, while changing the distancebetween the first mirror portion 31 and the second mirror portion 32 inthe Fabry-Perot interference filter 1).

As illustrated in FIG. 4, the dummy filter 2 is different from theFabry-Perot interference filter 1 described above in that the pluralityof through-holes 24 b is not formed in the second laminate 24 and thegap S is not formed in the intermediate layer 23. In the dummy filter 2,an intermediate layer 23 is provided between the first mirror portion 31and the second mirror portion 32. That is, the second mirror portion 32is disposed on the surface 23 a of the intermediate layer 23, notfloating above the gap S.

[Wafer Configuration]

Next, a configuration of a wafer according to an embodiment will bedescribed. As illustrated in FIGS. 5 and 6, a wafer 100 includes asubstrate layer 110. The substrate layer 110 has a disk shape with adiameter of approximately 150 mm or 200 mm, with an orientation flat OFformed in a portion of the substrate layer 110. For example, thesubstrate layer 110 is formed of silicon, quartz, glass, or the like.Hereinafter, a virtual straight line that passes through the center ofthe substrate layer 110 when viewed in the thickness direction of thesubstrate layer 110 and is parallel to the orientation flat OF isreferred to as a first straight line 3, while a virtual straight linethat passes through the center of the substrate layer 110 when viewed inthe thickness direction of the substrate layer 110 and is perpendicularto the orientation flat OF is referred to as a second straight line 4.

The wafer 100 includes an effective area 101 and a dummy area 102. Thedummy area 102 is an area along an outer edge 110 c of the substratelayer 110 (that is, the outer edge 100 a of the wafer 100). Theeffective area 101 is an area inside the dummy area 102. The dummy area102 surrounds the effective area 101 when viewed in the thicknessdirection of the substrate layer 110. The dummy area 102 is adjacent tothe effective area 101.

The effective area 101 includes a plurality of two-dimensionallyarranged Fabry-Perot interference filter portions 1A. The plurality ofFabry-Perot interference filter portions 1A is provided in the entireeffective area 101. The dummy area 102 includes a plurality oftwo-dimensionally arranged dummy filter portions 2A. The plurality ofdummy filter portions 2A is provided in an area of the dummy area 102excluding a pair of areas 102 a. One area 102 a is an area along theorientation flat OF. The other area 102 a is an area along the portionof the outer edge 110 c of the substrate layer 110 at an opposite sideof the orientation flat OF. The Fabry-Perot interference filter portion1A and the dummy filter portion 2A are adjacent to each other at aboundary between the effective area 101 and the dummy area 102. Whenviewed in the thickness direction of the substrate layer 110, the outershape of the Fabry-Perot interference filter portion 1A and the outershape of the dummy filter portion 2A are the same. The plurality ofFabry-Perot interference filter portions 1A and the plurality of dummyfilter portions 2A are arranged so as to be symmetric about each of thefirst straight line 3 and the second straight line 4 orthogonal to eachother. The plurality of dummy filter portions 2A may be provided overthe entire dummy area 102. Furthermore, the plurality of dummy filterportions 2A may be provided in an area other than one of the areas 102 ain the dummy areas 102.

Each of the plurality of Fabry-Perot interference filter portions 1A isto be each of a plurality of Fabry-Perot interference filters 1 when thewafer 100 is cut along each of lines 5. Each of the plurality of dummyfilter portions 2A is to be each of a plurality of dummy filters 2 whenthe wafer 100 is cut along each of the lines 5. When viewed in thethickness direction of the substrate layer 110, the plurality of lines 5extends in a direction parallel to the orientation flat OF, and theplurality of lines 5 extends in a direction perpendicular to theorientation flat OF. As an example, when each of the filter portions 1Aand 2A has a rectangular shape when viewed in the thickness direction ofthe substrate layer 110, each of the filter portions 1A and 2A isarranged in a two-dimensional matrix, and the plurality of lines 5 isset in a lattice pattern so as to pass between adjacent filter portions1A-1A, between adjacent filter portions 1A-2A, and between adjacentfilter portions 2A-2A.

(a) of FIG. 7 is a cross-sectional view of the Fabry-Perot interferencefilter portion 1A. (b) of FIG. 7 is a cross-sectional view of the dummyfilter portion 2A. As illustrated in (a) and (b) of FIG. 7, thesubstrate layer 110 is a layer that is to be a plurality of substrates11 when the wafer 100 is cut along each of the lines 5. The substratelayer 110 has a first surface 110 a and a second surface 110 b oppositeto the first surface 110 a. A reflection prevention layer 210 isprovided on the first surface 110 a of the substrate layer 110. Thereflection prevention layer 210 is a layer to be a plurality ofreflection prevention layers 21 when the wafer 100 is cut along each ofthe lines 5. A reflection prevention layer 410 is provided on the secondsurface 110 b of the substrate layer 110. The reflection preventionlayer 410 is a layer to be a plurality of antireflection layers 41 whenthe wafer 100 is cut along each of the lines 5.

A device layer 200 is provided on the reflection prevention layer 210.The device layer 200 includes a first mirror layer 220, an intermediatelayer 230, and a second mirror layer 240. The first mirror layer 220 isa layer having a plurality of first mirror portions 31, and is a layerto be a plurality of first laminates 22 when the wafer 100 is cut alongeach of the lines 5. The plurality of first mirror portions 31 istwo-dimensionally arranged on the first surface 110 a of the substratelayer 110 via the reflection prevention layer 210. The intermediatelayer 230 is a layer to be a plurality of intermediate layers 23 whenthe wafer 100 is cut along each of the lines 5. The second mirror layer240 is a layer having a plurality of second mirror portions 32, and is alayer to be a plurality of second laminates 24 when the wafer 100 is cutalong each of the lines 5. The plurality of second mirror portions 32 istwo-dimensionally arranged on the first mirror layer 220 via theintermediate layer 23.

A stress adjustment layer 400 is provided on the reflection preventionlayer 410. That is, the stress adjustment layer 400 is provided on thesecond surface 110 b of the substrate layer 110 via the reflectionprevention layer 410. The stress adjustment layer 400 includes aplurality of layers 420, 430, and 440. The layer 420 is a layer that isto be a plurality of third laminates 42 when the wafer 100 is cut alongeach of the lines 5. The layer 430 is a layer to be a plurality ofintermediate layers 43 when the wafer 100 is cut along each of the lines5. The layer 440 is a layer to be a plurality of fourth laminates 44when the wafer 100 is cut along each of the lines 5.

A light shielding layer 450 and a protective layer 460 are provided onthe stress adjustment layer 400. The light shielding layer 450 is alayer that is to be a plurality of light shielding layers 45 when thewafer 100 is cut along each of the lines 5. The protective layer 460 isa layer that is to be a plurality of protective layers 46 when the wafer100 is cut along each of the lines 5.

As illustrated in (a) of FIG. 7, each of the Fabry-Perot interferencefilter portions 1A has a gap S formed between the first mirror portion31 and the second mirror portion 32 facing each other. That is, in eachof the Fabry-Perot interference filter portions 1A, the intermediatelayer 23 defines the gap S, and the second mirror portion 32 floats onthe gap S. Similarly to the configuration of the Fabry-Perotinterference filter 1 described above, each of the Fabry-Perotinterference filter portions 1A includes a configuration related to thefirst electrode 12, the second electrode 13, the third electrode 14, theplurality of terminals 15 and 16, the opening 40 a, and the like.Therefore, even when the plurality of Fabry-Perot interference filterportions 1A is still in the state of the wafer 100, applying a voltageto each of the Fabry-Perot interference filter portions 1A via the pairof terminals 15 and 16 would change the distance between the firstmirror portion 31 and the second mirror portion 32 facing each other dueto the electrostatic force.

As illustrated in (b) of FIG. 7, each of the dummy filter portions 2Aincludes the intermediate layer 23 provided between the first mirrorportion 31 and the second mirror portion 32 facing each other. That is,in the dummy filter portion 2A, the intermediate layer 23 does notdefine the gap S, and the second mirror portion 32 is disposed on thesurface 23 a of the intermediate layer 23. Accordingly, although each ofthe dummy filter portions 2A has a configuration related to the firstelectrode 12, the second electrode 13, the third electrode 14, theplurality of terminals 15 and 16, the openings 40 a, and the like,similarly to the configuration of the dummy filter 2 described above,the distance between the first mirror portion 31 and the second mirrorportion 32 facing each other would not change. Note that each of thedummy filter portions 2A does not need to include the configurationrelated to the first electrode 12, the second electrode 13, the thirdelectrode 14, the plurality of terminals 15 and 16 (a metal film such asaluminum to form each of the terminal 15 and 16, through-holes fordisposing each of the terminals 15 and 16, and the like), the opening 40a, and the like.

As illustrated in FIG. 6 and (a) of FIG. 7, the device layer 200 has afirst groove 290 opening on the side opposite to the substrate layer110. The first groove 290 is formed along each of the lines 5. The firstgroove 290 surrounds the first mirror portion 31, the intermediate layer23, and the second mirror portion 32 in each of the Fabry-Perotinterference filter portions 1A and each of the dummy filter portions2A. In each of the Fabry-Perot interference filter portions 1A, thefirst mirror portion 31, the intermediate layer 23, and the secondmirror portion 32 are surrounded by the annularly continuous firstgroove 290. Similarly, in each of the dummy filter portions 2A, thefirst mirror portion 31, the intermediate layer 23, and the secondmirror portion 32 are surrounded by the annularly continuous firstgroove 290. Focusing on the adjacent filter portions 1A-1A, the adjacentfilter portions 1A-2A, and the adjacent filter portions 2A-2A, the firstgroove 290 corresponds to a region on a peripheral edge portion 34 ofone filter portion and a peripheral edge portion 34 of the other filterportion. The first groove 290 is continuous through the effective area101 and the dummy area 102, and reaches the outer edge 110 c of thesubstrate layer 110 when viewed in a direction in which the first mirrorportion 31 and the second mirror portion 32 face each other(hereinafter, simply referred to as a “facing direction”). It issufficient as long as the first groove 290 surrounds at least the secondmirror portion 32 in each of the Fabry-Perot interference filterportions 1A and each of the dummy filter portions 2A. In this case, thesecond mirror portion 32 in the facing direction does not need to besurrounded, as a whole, by the first groove 290. It is sufficient aslong as at least a portion of the second mirror portion 32 in the facingdirection is surrounded by the first groove 290.

As illustrated in (b) of FIG. 7, the stress adjustment layer 400 has asecond groove 470 opening on the opposite side of the substrate layer110. The second groove 470 is formed along each of the lines 5. That is,the second groove 470 is formed so as to correspond to the first groove290. Here, formation of the second groove 470 corresponding to the firstgroove 290 means that the second groove 470 overlaps the first groove290 when viewed in the facing direction. Therefore, the second groove470 is continuous in the effective area 101 and the dummy area 102 andreaches the outer edge 110 c of the substrate layer 110 when viewed inthe facing direction.

[Method of Manufacturing Wafer]

Next, a method of manufacturing the wafer 100 will be described withreference to FIGS. 8 to 13. In FIGS. 8 to 13, (a) is cross-sectionalview of a portion corresponding to the Fabry-Perot interference filterportion 1A, and (b) is a cross-sectional view of a portion correspondingto the dummy filter portion 2A.

First, as illustrated in FIG. 8, the reflection prevention layer 210 isformed on the first surface 110 a of the substrate layer 110, while thereflection prevention layer 410 is formed on the second surface 110 b ofthe substrate layer 110. Subsequently, a plurality of polysilicon layersand a plurality of silicon nitride layers are alternately laminated oneach of the reflection prevention layers 210 and 410, so as to form thefirst mirror layer 220 on the reflection prevention layer 210 and formthe layer 420 on the reflection prevention layer 410.

When the first mirror layer 220 is formed, etching is performed toremove a portion along each of the lines 5 in the first mirror layer 220so as to expose the surface of the reflection prevention layer 210. Inaddition, by doping impurities to achieve low resistivity in a portionof a predetermined polysilicon layer in the first mirror layer 220, thefirst electrode 12, the second electrode 13, and the wiring 12 a and 13a are formed in each of portions corresponding to the substrate 11.Moreover, etching is performed to form the trenches 17 and 18 on asurface of the first mirror layer 220 in each of portions correspondingto the substrate 11.

Subsequently, as illustrated in FIG. 9, the intermediate layer 230 isformed on the first mirror layer 220 and on the exposed surface of thereflection prevention layer 210, and the layer 430 is formed on thelayer 420. At a portion corresponding to each of the Fabry-Perotinterference filter portions 1A, the intermediate layer 230 includes aportion 50 expected to be removed corresponding to the gap S (refer toFIG. 3). Subsequently, etching is performed to remove a portion alongeach of the lines 5 in the intermediate layer 230 and the reflectionprevention layer 210 so as to expose the first surface 110 a of thesubstrate layer 110. In addition, the etching is performed to form a gapat a portion corresponding to each of the terminals 15 and 16 (refer toFIG. 3) in the intermediate layer 230 for each of portions correspondingto the substrate 11.

Subsequently, as illustrated in FIG. 10, a plurality of polysiliconlayers and a plurality of silicon nitride layers are alternatelylaminated on each of the first surface 110 a side and the second surface110 b side of the substrate layer 110, thereby forming the second mirrorlayer 240 on the intermediate layer 230 and on the exposed first surface110 a of the substrate layer 110, as well as forming the layer 440 onthe layer 430.

When the second mirror layer 240 is formed, side surfaces 230 a of theintermediate layer 230, side surfaces 220 a of the first mirror layer220, and side surfaces 210 a of the reflection prevention layer 210,facing each other along the line 5, are covered with the second mirrorlayer 240. In addition, by doping impurities to achieve low resistivityin a portion of a predetermined polysilicon layer in the second mirrorlayer 240, the third electrode 14 and the wiring 14 a are formed in eachof portions corresponding to the substrate 11.

Subsequently, as illustrated in FIG. 11, etching is performed to thin aportion along each of the lines 5 in the second mirror layer 240 so asto expose the surface of the polysilicon layer 27 a (refer to FIG. 3)(that is, the polysilicon layer positioned closest to the first surface110 a side) included in the second mirror layer 240. In addition, theetching is performed to form a gap at a portion corresponding to each ofthe terminals 15 and 16 (refer to FIG. 3) in the second mirror layer 240for each of portions corresponding to the substrate 11. Subsequently,the terminals 15 and 16 are formed in the gap for each of portionscorresponding to the substrate 11, and the terminal 15 and the wiring 12a are connected to each other, while the terminal 16 and each of thewiring 13 a and the wiring 14 a are connected to each other.

With the procedure above, the reflection prevention layer 210 and thedevice layer 200 are formed on the first surface 110 a of the substratelayer 110, while the first groove 290 is formed in the device layer 200.The first groove 290 is a region where the device layer 200 is partiallythinned along each of the lines 5.

Subsequently, as illustrated in (a) of FIG. 12, etching is performed ineach of portions corresponding to the Fabry-Perot interference filterportion 1A so as to form, in the second laminate 24, the plurality ofthrough-holes 24 b from the surface 24 a of the second laminate 24 tothe portion 50 expected to be removed. At this time, as illustrated in(b) of FIG. 12, the plurality of through-holes 24 b will not be formedin the second laminate 24 in a portion corresponding to each of thedummy filter portions 2A. Subsequently, as illustrated in FIG. 12, thelight shielding layer 450 is formed on the layer 440. Subsequently,etching is performed to remove a portion along each of the lines 5 inthe light shielding layer 450 and the stress adjustment layer 400 (thatis, the layers 420, 430, and 440) so as to expose the surface of thereflection prevention layer 410. In addition, the etching is performedto form the opening 40 a in each of portions corresponding to thesubstrate 11. Subsequently, the protective layer 460 is formed on thelight shielding layer 450, the exposed surface of the reflectionprevention layer 410, an inner surface of the opening 40 a, and the sidesurface of the stress adjustment layer 400 facing the second groove 470.

With the procedure above, the reflection prevention layer 410, thestress adjustment layer 400, the light shielding layer 450, and theprotective layer 460 are formed on the second surface 110 b of thesubstrate layer 110, while the second groove 470 is formed in the stressadjustment layer 400. The second groove 470 is a region in which thestress adjustment layer 400 is partially thinned along each of the lines5.

Subsequently, as illustrated in (a) of FIG. 13, etching via a pluralityof through-holes 24 b (for example, gas phase etching using hydrofluoricacid gas) is performed at a portion corresponding to each of theFabry-Perot interference filter portions 1A to collectively remove theplurality of portions 50 expected to be removed from the intermediatelayer 230. With this procedure, a gap S is formed in the portioncorresponding to each of the Fabry-Perot interference filter portions 1Afor each of portion corresponding to the substrate 11. At this time, asillustrated in (b) of FIG. 13, since the plurality of through-holes 24 bis not formed in the second laminate 24 at the portion corresponding toeach of the dummy filter portions 2A, the gap S will not be formed inthe intermediate layer 230.

With the procedure described above, as illustrated in (a) of FIG. 7, thegap S is formed between the first mirror portion 31 and the secondmirror portion 32 facing each other in the effective area 101, therebyforming the plurality of Fabry-Perot interference filter portions 1A. Incontrast, in the dummy area 102, the intermediate layer 23 is providedbetween the first mirror portion 31 and the second mirror portion 32facing each other as illustrated in (b) of FIG. 7, thereby forming theplurality of dummy filter portion 2A.

[Method of Manufacturing Fabry-Perot Interference Filter]

Next, a method for cutting out the Fabry-Perot interference filter 1from the wafer 100 (a method of manufacturing the Fabry-Perotinterference filter 1) will be described with reference to FIGS. 14 and15. In FIGS. 14 and 15, (a) is cross-sectional view of a portioncorresponding to the Fabry-Perot interference filter portion 1A, and (b)is a cross-sectional view of a portion corresponding to the dummy filterportion 2A.

First, as illustrated in FIG. 14, an expanding tape 60 is attached ontothe protective layer 460 (that is, to the second surface 110 b side).Subsequently, laser light L is applied from a side opposite to theexpanding tape 60 in a state where the expanding tape 60 is attached tothe second surface 110 b side, and then a converging point of the laserlight L is relatively moved along each of the lines 5 while theconverging point of the laser light L is positioned within the substratelayer 110. That is, the laser light L is controlled to be incident onthe substrate layer 110 from the side opposite to the expanding tape 60through the surface of the polysilicon layer exposed in the first groove290.

With the irradiation of the laser light L, a modified region 7 is formedwithin the substrate layer 110 along each of the lines 5. The modifiedregion 7 is a region having physical characteristics such as density, arefractive index, mechanical strength different from those in thesurrounding area, and is a region to be a start point of a fractureextending in a thickness direction of the substrate layer 110. Examplesof the modified region 7 include molten processed regions (which meansat least any one of a region resolidified after melting, a region in amelted state, and a region in a state of being resolidified from themelted state), a crack region, a dielectric breakdown region, arefractive index changed region, or the like, or a mixed region ofthese. Further examples of the modified region 7 include a region wherethe density of the modified region 7 has changed from that of anunmodified region, a region with a lattice defect, or the like, in thematerial of the substrate layer 110. When the material of the substratelayer 110 is monocrystalline silicon, the modified region 7 can also bedefined as a high-dislocation density region. The number of rows of themodified regions 7 arranged in the thickness direction of the substratelayer 110 with respect to each of the lines 5 is appropriately adjustedbased on the thickness of the substrate layer 110.

Subsequently, as illustrated in FIG. 15, the expanding tape 60 attachedto the second surface 110 b side is expanded so as to extend thefracture in the thickness direction of the substrate layer 110 from themodified region 7 formed within the substrate layer 110, and then, thesubstrate layer 110 is cut into the plurality of substrates 11 alongeach of the lines 5. At this time, the polysilicon layer of the secondmirror layer 240 is cut along each of the lines 5 in the first groove290, while the reflection prevention layer 410 and the protective layer460 are cut along each of the lines 5 in the second groove 470. Withthis procedure, a plurality of Fabry-Perot interference filters 1 andthe plurality of dummy filters 2 in a state of being separated from eachother on the expanding tape 60 are obtained.

[Configuration of Light Detection Device]

Next, a configuration of the light detection device 10 including theFabry-Perot interference filter 1 will be described. As illustrated inFIG. 16, the light detection device 10 includes a package 71. Thepackage 71 is a CAN package including a stem 72 and a cap 73. The cap 73is integrally formed by a side wall 74 and a top wall 75. The stem 72and the cap 73 are formed of a metal material and are hermeticallyjoined to each other. In the package 71 formed of a metal material, theshape of the side wall 74 is cylindrical about a line 9 as a centerline. The stem 72 and the top wall 75 face each other in a directionparallel to the line 9, and close both ends of the side wall 74,individually.

A wiring substrate 76 is secured to an inner surface 72 a of the stem72. Examples of a material applicable as the wiring substrate 76 includesilicon, ceramic, quartz, glass, plastic, or the like. The lightdetector (light detection unit) 77 and a temperature detector (notillustrated) such as a thermistor are mounted on the wiring substrate76. The light detector 77 is disposed on the line 9. More specifically,the light detector 77 is disposed such that the center line of a lightreceiving portion thereof is aligned with the line 9. The light detector77 is an infrared detector such as a quantum type sensor using InGaAs orother compounds or a thermal type sensor using a thermopile or abolometer or the like. In a case of detecting light of differentwavelength bands of ultraviolet, visible, and near infrared regions, forexample a silicon photodiode or the like can be used as the lightdetector 77. Note that the light detector 77 may include one lightreceiving portion, or a plurality of light receiving portions providedin an array. Furthermore, a plurality of light detectors 77 may bemounted on the wiring substrate 76. The temperature detector may bedisposed at a position close to the Fabry-Perot interference filter 1,for example, so that a temperature change of the Fabry-Perotinterference filter 1 can be detected.

A plurality of spacers 78 is secured onto the wiring substrate 76.Examples of a material applicable as the spacers 78 include silicon,ceramic, quartz, glass, plastic, or the like. The Fabry-Perotinterference filter 1 is secured onto the plurality of spacers 78 byadhesive, for example. Fabry-Perot interference filter 1 is disposed onthe line 9. More specifically, the Fabry-Perot interference filter 1 isdisposed such that the center line of the light transmission region 1 ais aligned with the line 9. Note that the spacers 78 may be integrallyformed with the wiring substrate 76. The Fabry-Perot interference filter1 may be supported by a single spacer 78, rather than by the pluralityof spacers 78.

A plurality of lead pins 81 is secured to the stem 72. Morespecifically, each of the lead pins 81 penetrates through the stem 72 ina state where electrical insulation and hermeticity with the stem 72 aremaintained. Each of the lead pins 81 is electrically connected by wires82 to each of electrode pads provided on the wiring substrate 76, aterminal of the light detector 77, a terminal of the temperaturedetector, and a terminal of the Fabry-Perot interference filter 1. Thelight detector 77, the temperature detector, and the Fabry-Perotinterference filter 1 may be electrically connected to each of the leadpin 81 via the wiring substrate 76. For example, each of terminals maybe electrically connected to an electrode pad provided on the wiringsubstrate 76, while the electrode pad and each of the lead pins 81 maybe connected by the wire 82. This enables input and output of electricsignals to and from each of the light detector 77, the temperaturedetector, and the Fabry-Perot interference filter 1.

The package 71 has an opening 71 a. More specifically, the opening 71 ais formed in the top wall 75 of the cap 73 such that the center linethereof is aligned with the line 9. The shape of the opening 71 a iscircular when viewed in a direction parallel to the line 9. A lighttransmitting member 83 is disposed on an inner surface 75 a of the topwall 75 so as to close the opening 71 a. The light transmitting member83 is hermetically joined to the inner surface 75 a of the top wall 75.The light transmitting member 83 has a light incident surface 83 a and alight emission surface 83 b (inner surface) opposite to the lightincident surface 83 a in a direction parallel to line 9, and has sidesurfaces 83 c. The light incident surface 83 a of the light transmittingmember 83 is substantially flush with an outer surface of the top wall75 at the opening 71 a. The side surface 83 c of the light transmittingmember 83 is in contact with an inner surface 74 a of the side wall 74of the package 71. That is, the light transmitting member 83 reaches theinside of the opening 71 a and the inner surface 74 a of the side wall74. Such a light transmitting member 83 is formed by disposing a glasspellet inside the cap 73 with the opening 71 a facing down and meltingthe glass pellet. That is, the light transmitting member 83 is formed offused glass.

A band pass filter 84 is secured to the light emission surface 83 b ofthe light transmitting member 83 by a bonding member 85. That is, thebonding member 85 secures the band pass filter 84 to the inner surface75 a of the top wall 75 via the light transmitting member 83 joined tothe inner surface 75 a of the top wall 75. The band pass filter 84selectively transmits light with a measurement wavelength range by thelight detection device 10 (light with a predetermined wavelength rangeand should be incident on the light transmission region 1 a of theFabry-Perot interference filter 1) out of light transmitted through thelight transmitting member 83 (that is, the band pass filter 84 transmitsonly the light with the wavelength range). The band pass filter 84 has arectangular plate shape. More specifically, the band pass filter 84 hasa light incident surface 84 a and a light emission surface 84 b oppositeto the light incident surface 84 a in a direction parallel to the line9, and has four side surfaces 84 c. The band pass filter 84 is obtainedby forming a dielectric multilayer film (for example, a multilayer filmcombining a high refractive material such as TiO₂, Ta₂O₅, or the likeand a low refractive material such as SiO₂, MgF₂, or the like) on asurface of a light transmitting member formed in a rectangular shapeusing a light transmitting material (for example, silicon, glass, or thelike).

The bonding member 85 includes a first portion 85 a arranged over theentire region of the light incident surface 84 a of the band pass filter84. That is, the first portion 85 a in the bonding member 85 is aportion arranged between the light emission surface 83 b of the lighttransmitting member 83 and the light incident surface 84 a of the bandpass filter 84 facing each other. The bonding member 85 further includesa second portion 85 b protruding outward from the outer edge of the bandpass filter 84 when viewed in a direction parallel to the line 9. Thesecond portion 85 b reaches the inner surface 74 a of the side wall 74and is in contact with the inner surface 74 a of the side wall 74.Furthermore, the second portion 85 b is in contact with the side surface84 c of the band pass filter 84.

In the light detection device 10 configured as described above, whenlight is incident on the band pass filter 84 from outside via theopening 71 a, the light transmitting member 83, and the bonding member85, light with a predetermined wavelength range is selectivelytransmitted. When the light transmitted through the band pass filter 84is incident on the light transmission region 1 a of the Fabry-Perotinterference filter 1, light with a predetermined wavelength out of thelight with the predetermined wavelength range is selectivelytransmitted. The light transmitted by the light transmission region 1 aof the Fabry-Perot interference filter 1 is incident on the lightreceiving portion of the light detector 77 and is detected by the lightdetector 77. That is, the light detector 77 converts the lighttransmitted through the Fabry-Perot interference filter 1 into anelectric signal and outputs the electric signal. For example, the lightdetector 77 outputs an electric signal of a strength corresponding tothe intensity of the light incident on the light receiving portion.

[Action and Effect by Wafer]

The wafer 100 enables acquisition of a plurality of Fabry-Perotinterference filters 1 with high efficiency and high yield as describedbelow.

In the wafer 100, the plurality of Fabry-Perot interference filterportions 1A to be the plurality of Fabry-Perot interference filters 1 isprovided in the effective area 101. In addition, the plurality of dummyfilter portions 2A is provided in the dummy area 102 desposed along theouter edge 110 c of the substrate layer 110 and surrounding theeffective area 101, and the intermediate layer 23 is provided betweenthe first mirror portion 31 and the second mirror portion 32 facing eachother in each of the dummy filter portions 2A. This configurationsufficiently ensures the strength of the entire wafer 100. Thisfacilitates handling of the wafer 100 when cutting out a plurality ofFabry-Perot interference filters 1 from the wafer 100, for example.Furthermore, each of the Fabry-Perot interference filter portions 1Aoperates similarly to the Fabry-Perot interference filter 1 even whenthe plurality of Fabry-Perot interference filter portions 1A is still inthe state of the wafer 100. Accordingly, it is possible to inspectvarious characteristics of each of the Fabry-Perot interference filterportions 1A in this state, with improved easiness of handling of thewafer 100 during execution of such an inspection. The presence of thegap S formed between the first mirror portion 31 and the second mirrorportion 32 facing each other in each of the dummy filter portions 2Awould lead to a case, for example, where the second mirror portion 32 isdamaged when the dummy area 102 of the wafer 100 is gripped by a grippertool and fragments of the second mirror portion 32 would adhere to theFabry-Perot interference filter portion 1A to degrade the appearance andcharacteristics of the Fabry-Perot interference filter portion 1A.Occurrence of such a situation is suppressed in this wafer 100 becauseit includes the intermediate layer 23 provided between the first mirrorportion 31 and the second mirror portion 32 facing each other in each ofthe dummy filter portions 2A.

In the wafer 100, at least the second mirror portion 32 is surrounded bythe first groove 290 in each of the Fabry-Perot interference filterportions 1A. This improves the yield in cutting out the plurality ofFabry-Perot interference filters 1 from the wafer 100. In a case whereat least the second mirror portion 32 is not surrounded by the firstgroove 290 in each of the Fabry-Perot interference filter portions 1A,peeling, chipping, or the like are likely to occur at a cutting surfaceof the device layer 200 when the plurality of Fabry-Perot interferencefilters 1 is cut out from the wafer 100, and this might causedegradation of the appearance, characteristics, or the like in theFabry-Perot interference filter portion 1A.

In the wafer 100, at least the second mirror portion 32 is surrounded bythe first groove 290 in each of the dummy filter portions 2A. In a casewhere at least the second mirror portion 32 is not surrounded by thefirst groove 290 in each of the dummy filter portions 2A, no gap isformed between the first mirror portion 31 and the second mirror portion32, which would lead to accumulation of stress in the dummy filterportion 2A and might cause warpage of the wafer 100. In the wafer 100,since at least the second mirror portion 32 is surrounded by the firstgroove 290 in each of the dummy filter portions 2A, the stress isreduced in the dummy area 102, and the warpage of the wafer 100 issuppressed. In a case where at least the second mirror portion 32 is notsurrounded by the first groove 290 in each of the dummy filter portions2A, peeling, chipping, or the like are likely to occur at a cuttingsurface of the device layer 200 when the plurality of dummy filters 2 iscut out from the wafer 100, resulting in adhesion of fragments to theFabry-Perot interference filter 1, which might cause degradation of theappearance, characteristics, or the like in the Fabry-Perot interferencefilter 1. Occurrence of such a situation is suppressed in the wafer 100because at least the second mirror portion 32 is surrounded by the firstgroove 290 in each of the dummy filter portions 2A.

In the wafer 100, the first groove 290 is continuous through theeffective area 101 and the dummy area 102, and reaches the outer edge110 c of the substrate layer 110 when viewed in the facing direction.With this configuration, it is possible to further improve the yield atthe time of cutting out a plurality of Fabry-Perot interference filters1 from the wafer 100, and possible to further reliably suppress thewarpage of the wafer 100.

In the wafer 100, the stress adjustment layer 400 is provided on thesecond surface 110 b of the substrate layer 110, and the second groove470 is formed in the stress adjustment layer 400 so as to correspond tothe first groove 290. With this configuration, it is possible to furtherimprove the yield at the time of cutting out a plurality of Fabry-Perotinterference filters 1 from the wafer 100, and possible to furtherreliably suppress the warpage of the wafer 100. In a case where thesecond groove 470 is not formed in the stress adjustment layer 400 so asto correspond to the first groove 290, peeling, chipping, or the likeare likely to occur at a cutting surface of the stress adjustment layer400 when the plurality of Fabry-Perot interference filters 1 and theplurality of dummy filters 2 are cut out from the wafer 100, and thismight cause degradation of the appearance, characteristics, or the likein the Fabry-Perot interference filter 1. Occurrence of such a situationis suppressed in the wafer 100 because the second groove 470 is formedin the stress adjustment layer 400 so as to correspond to the firstgroove 290.

In the wafer 100, the plurality of Fabry-Perot interference filterportions 1A and the plurality of dummy filter portions 2A are arrangedso as to be symmetric with respect to the first straight line 3 and thesecond straight line 4 which are orthogonal to each other. This makes itpossible to more reliably suppress the warpage of the entire wafer 100.

In a method of manufacturing the wafer 100, the gap S is formed in eachof the Fabry-Perot interference filter portions 1A while the pluralityof Fabry-Perot interference filter portions 1A is still in the state ofthe wafer 100. Accordingly, compared to a case of forming the gap Sindividually at a chip level, it is possible to form the gap S betweenthe first mirror portion 31 and the second mirror portion 32 withsignificantly higher efficiency. Furthermore, since a process proceedssimultaneously in the effective area 101 at a portion corresponding toan arbitrary substrate 11 within the substrate layer 110 and portionscorresponding to the surrounding substrates around the substrate 11,such as in the etching of the intermediate layer 230 simultaneouslyperformed onto the plurality of two-dimensionally arranged portions 50expected to be removed, it is possible to reduce an unevenness ofin-plane stress in the substrate layer 110. Therefore, according to themethod of manufacturing the wafer 100, it is possible to obtain thewafer 100 capable of stable mass-production of high-quality Fabry-Perotinterference filters 1.

Furthermore, irradiation of the laser light L to form the modifiedregion 7 inside the substrate layer 110 along each of the lines 5 andthereby cutting the wafer 100 along each of the lines 5 will beextremely effective in manufacturing the Fabry-Perot interference filter1 for the following reasons. That is, cutting the wafer 100 using thelaser light L needs no water and thus can suppress an incidence ofdamage onto the second mirror portion 32 floating on the gap S by waterpressure and suppress sticking (phenomenon of stoppage of the secondmirror portion 32 due to contact with the first mirror portion 31)caused by water intrusion into the gap S. Therefore, cutting the wafer100 using the laser light L is extremely effective in manufacturing theFabry-Perot interference filter 1.

[Modifications]

Although an embodiment of the present disclosure has been described asabove, the present disclosure is not limited to the embodiment describedabove. For example, the material and the shape of each configuration arenot limited to the materials and the shapes described above, and it ispossible to employ various materials and shapes. In the wafer 100, whenviewed in the thickness direction of the substrate layer 110, the outershape of the Fabry-Perot interference filter portion 1A and the outershape of the dummy filter portion 2A need not be the same. Furthermore,when cutting out a plurality of Fabry-Perot interference filters 1 fromthe wafer 100, there is no need to cut out all the dummy filter portions2A (that is, it is not necessary to singulate all the dummy filterportions 2A).

Furthermore, as illustrated in FIG. 14, the wafer 100 may include themodified region 7 formed inside the substrate layer 110 so as tocorrespond to the first groove 290. Here, forming the modified region 7so as to correspond to the first groove 290 means that the modifiedregion 7 is formed to overlap the first groove 290 when viewed in thefacing direction, and in particular, means the modified region 7 isformed along each of the lines 5. This enables the fracture to beextended from the modified region 7 in a thickness direction of thesubstrate layer 110, making it possible to easily and accurately cut outa plurality of Fabry-Perot interference filters 1 from the wafer 100. Inthis case, the expanding tape 60 may be attached to the second surface110 b side of the substrate layer 110. At this time, the outer edgeportion of the expanding tape 60 attached to the wafer 100 is held by anannular frame. This facilitates handling of the wafer 100 even in astate where the modified region 7 is formed inside the substrate layer110. In the wafer 100 in which the modified region 7 is formed insidethe substrate layer 110, there is a possibility that a fracture mayunexpectedly extend from the modified region 7. In the wafer 100, theplurality of dummy filter portions 2A, the first groove 290, and thesecond groove 470 are not provided in the pair of areas 102 a of thedummy area 102. This can suppress the occurrence of a fracture and evenwhere a fracture develops, the extension of the fracture would bestopped by the pair of areas 102 a.

Furthermore, as illustrated in FIG. 17, a mirror-removed portion 2X maybe formed in a portion of the dummy area 102. The mirror-removed portion2X is formed by exposing the surface of the first mirror portion 31without providing the second mirror portion 32 and the intermediatelayer 23 (refer to (b) of FIG. 19). That is, the mirror-removed portion2X differs from the dummy filter portion 2A in that the second mirrorportion 32 and the intermediate layer 23 are not provided. In the wafer100 illustrated in FIG. 17, a plurality of the mirror-removed portions2X is provided in an annular region (region outside the broken line inFIG. 17) along the outer edge 110 c of the substrate layer 110. Themirror-removed portion 2X is not limited to the one obtained by removingall of the second mirror portion 32 and the intermediate layer 23. It isallowable to obtain the mirror-removed portion 2X by removing at least aportion of the second mirror portion 32. That is, the mirror-removedportion 2X has a configuration in which a portion of the second mirrorportion 32 is removed as a layer from the surface on the side oppositeto the first mirror portion 31 and this removal leads to the absence ofa layer on the first mirror portion 31 or thinning of the layer on thefirst mirror portion 31. In the mirror-removed portion 2X, not only thelaminate on the first surface 110 a side of the substrate layer 110 butalso the laminate on the second surface 110 b side of the substratelayer 110 may be thinned. For example, it is allowable to eliminate thestress adjustment layer 400 or thin the stress adjustment layer 400.

In the wafer 100 illustrated in FIG. 17, at least a portion of thesecond mirror portion 32 is removed from a portion of the dummy area102, thereby forming the mirror-removed portion 2X. With thisconfiguration, in a case where a plurality of through-holes 24 b is tobe formed in the second mirror portion 32 in a portion corresponding toeach of the Fabry-Perot interference filter portions 1A in order to formthe gap S by etching between the first mirror portion 31 and the secondmirror portion 32 facing each other, for example, it is possible, bymonitoring the removal state of the second mirror portion 32 in aportion corresponding to the mirror-removed portion 2X, to reliably formthe plurality of through-holes 24 b in the second mirror portion 32 at aportion corresponding to each of the Fabry-Perot interference filterportions 1A (details will be described below). This makes it possible toform the wafer 100 including a plurality of Fabry-Perot interferencefilter portions 1A in which the gap S is reliably formed between thefirst mirror portion 31 and the second mirror portion 32 facing eachother.

Furthermore, in the wafer 100 illustrated in FIG. 17, at least the firstmirror portion 31 is surrounded by the first groove 290 in themirror-removed portion 2X. This can reduce the stress also in themirror-removed portion 2X, suppressing the warpage of the wafer 100.

Furthermore, in the wafer 100 illustrated in FIG. 17, the mirror-removedportions 2X is provided in plurality along the outer edge 110 c of thesubstrate layer 110 in the dummy area 102, and the first groove 290 iscontinuous through the effective area 101 and the dummy area 102, so asto reach the outer edge 110 c of the substrate layer 110 when viewed inthe facing direction. As an example, the plurality of mirror-removedportions 2X is continuously arranged along the outer edge 110 c to forman area, and the area surrounds the effective area 101 and the dummyarea 102 excluding the formed area when viewed in the facing direction.With this configuration, the plurality of dummy filter portions 2A isarranged outside the plurality of Fabry-Perot interference filterportions 1A, and the plurality of mirror-removed portions 2X is arrangedoutside the plurality of dummy filter portions 2A, and the first groove290 is also continuous to reach the outer edge 110 c of the substratelayer 110, leading to improvement of the stress balance of the entirewafer 100, making it possible to further reliably suppress the warpageof the wafer 100.

An example of a method for manufacturing the wafer 100 illustrated inFIG. 17 will be described. First, as illustrated in FIGS. 8 to 11, thereflection prevention layer 210 and the device layer 200 are formed on afirst surface 110 a of a substrate layer 110, while the first groove 290is formed in the device layer 200. However, in a region where theplurality of mirror-removed portions 2X is provided (here, a regionoutside the broken line in FIG. 17), there is no need to provide aconfiguration related to the first electrode 12, the second electrode13, the third electrode 14, and the plurality of terminals 15 and 16 (ametal film such as aluminum to form each of the terminals 15 and 16,through-holes for disposing the terminals 15 and 16, and the like), theopening 40 a, and the like.

Subsequently, as illustrated in (a) of FIG. 18, etching is performed ineach of portions corresponding to the Fabry-Perot interference filterportion 1A so as to form, in the second laminate 24, the plurality ofthrough-holes 24 b from the surface 24 a of the second laminate 24 tothe portion 50 expected to be removed. Together with this procedure, asillustrated in (b) of FIG. 18, the mask is removed from portionscorresponding to the individual mirror-removed portions 2X, and etchingis performed to remove the second laminate 24. At this time, theemission spectrum of the plasma (emission of a specific wavelengthdepending on the material of the layer being etched) is monitored in aportion corresponding to each of the mirror-removed portions 2X in orderto determine the timing of completion of etching.

The reason why the emission spectrum of the plasma is monitored in theportion corresponding to each of the mirror-removed portions 2X is asfollows. That is, each of the through-holes 24 b is formed in a sizethat would not substantially influence the function of the second mirrorportion 32. Therefore, a change in the intensity of the emissionspectrum cannot be easily observed by monitoring the emission spectrumof the plasma emitted from the portion corresponding to each of thethrough-holes 24 b. To handle this, by monitoring the emission spectrumof the plasma in a portion corresponding to each of the mirror-removedportions 2X including the identical second laminate 24, it is possibleto accurately determine the timing of the completion of the etching,leading to high-accuracy formation of the plurality of through-holes 24b in the second laminate 24 in portions corresponding to each of theFabry-Perot interference filter portions 1A. Note that, as describedabove, the plurality of through-holes 24 b will not be formed in thesecond laminate 24 (refer to (b) of FIG. 12) in the portioncorresponding to each of the dummy filter portions 2A.

Subsequently, as illustrated in FIG. 18, a light shielding layer 450 isformed on the layer 440. Subsequently, etching is performed to remove aportion along each of the lines 5 in the light shielding layer 450 andthe stress adjustment layer 400 (that is, the layers 420, 430, and 440)so as to expose the surface of the reflection prevention layer 410. Inaddition, the etching is performed to form the opening 40 a in each ofportions corresponding to the substrate 11. Subsequently, the protectivelayer 460 is formed on the light shielding layer 450, the exposedsurface of the reflection prevention layer 410, an inner surface of theopening 40 a, and the side surface of the stress adjustment layer 400facing the second groove 470.

Subsequently, as illustrated in (a) of FIG. 19, etching via a pluralityof through-holes 24 b (for example, gas phase etching using hydrofluoricacid gas) is performed at a portion corresponding to each of theFabry-Perot interference filter portions 1A to collectively remove theplurality of portions 50 expected to be removed from the intermediatelayer 230. With this procedure, a gap S is formed in the portioncorresponding to each of the Fabry-Perot interference filter portions 1Afor each of portions corresponding to the substrate 11. At this time, asillustrated in (b) of FIG. 19, since the second laminate 24 has beenremoved in the portion corresponding to each of the mirror-removedportions 2X, the intermediate layer 23 has been removed to expose thesurface of the first mirror portion 31. Note that since the plurality ofthrough-holes 24 b is not formed in the second laminate 24 at theportion corresponding to each of the dummy filter portions 2A asdescribed above, the gap S will not be formed in the intermediate layer230 (refer to (b) of FIG. 13).

With the procedure described above, as illustrated in (a) of FIG. 7, thegap S is formed between the first mirror portion 31 and the secondmirror portion 32 facing each other in the effective area 101, therebyforming the plurality of Fabry-Perot interference filter portions 1A. Incontrast, in the dummy area 102, the intermediate layer 23 is providedbetween the first mirror portion 31 and the second mirror portion 32facing each other as illustrated in (b) of FIG. 7, thereby forming theplurality of dummy filter portion 2A. Furthermore, in a portion of thedummy area 102, the second mirror portion 32 and the intermediate layer23 are not provided, as illustrated in (b) of FIG. 19 so as to exposethe surface of the first mirror portion 31, thereby forming themirror-removed portion 2X.

REFERENCE SIGNS LIST

1: Fabry-Perot interference filter, 1A: Fabry-Perot interference filterportion, 2: dummy filter, 2A: dummy filter portion, 2X: mirror-removedportion, 3: first straight line, 4: second straight line, 7: modifiedregion, 23: intermediate layer, 31: first mirror portion, 32: secondmirror portion, 60: expanding tape, 100: wafer, 101: effective area,102: dummy area, 110: substrate layer, 110 a: first surface, 110 b:second surface, 110 c: outer edge, 220: first mirror layer, 240: secondmirror layer, 290: first groove, 400: stress adjustment layer, 470:second groove, S: gap.

1. A wafer comprising: a substrate layer having a first surface and asecond surface opposite to the first surface; a first mirror layerhaving a plurality of first mirror portions two-dimensionally arrangedon the first surface; and a second mirror layer having a plurality ofsecond mirror portions two-dimensionally arranged on the first mirrorlayer, wherein a plurality of Fabry-Perot interference filter portionsare formed in an effective area, in each of the plurality of Fabry-Perotinterference filter portions a gap is formed between the first mirrorportion and the second mirror portion facing each other and a distancebetween the first mirror portion and the second mirror portion facingeach other varies by an electrostatic force, a plurality of dummy filterportions are formed in a dummy area disposed along an outer edge of thesubstrate layer and surrounding the effective area, in each of theplurality of dummy filter portions an intermediate layer is providedbetween the first mirror portion and the second mirror portion facingeach other, and a groove extends along a boundary between the effectivearea and the dummy area, the groove opening on a side opposite to thesubstrate layer.
 2. The wafer according to claim 1, wherein the grooveincludes a plurality of straight portions, and each of the plurality ofstraight portions extends along two or more of the plurality ofFabry-Perot interference filter portions.
 3. The wafer according toclaim 1, wherein at least the second mirror portion is surrounded by afirst groove opening on a side opposite to the substrate layer in eachof the plurality of Fabry-Perot interference filter portions, and thegroove includes a part of the first groove.
 4. The wafer according toclaim 3, wherein the plurality of dummy filter portions is provided inan area of the dummy area excluding a first area and a second area, thefirst area is an area along an orientation flat formed at a portion ofthe substrate layer, the second area is an area along a part of theouter edge of the substrate layer on a side opposite to the orientationflat, and at least the second mirror portion is surrounded by the firstgroove in each of the plurality of dummy portions.
 5. The waferaccording to claim 1, further comprising a stress adjustment layerprovided on the second surface, wherein a second groove opening on anopposite side of the substrate layer is formed in the stress adjustmentlayer, and the second groove is formed so as to correspond to thegroove.
 6. The wafer according to claim 1, wherein the plurality ofFabry-Perot interference filter portions and the plurality of dummyfilter portions are disposed so as to be symmetric about each of a firststraight line and a second straight line passing through a center of thesubstrate layer and orthogonal to each other when viewed in thedirection in which the first mirror portion and the second mirrorportion face each other.